[28] Except through thinking and perceiving nothing is given to us directly. The question now arises: What is the significance of the percept, according to our line of argument? We have learnt that the proof which critical idealism offers of the subjective nature of perceptions collapses. But insight into the falsity of the proof is not alone sufficient to show that the doctrine itself is erroneous. Critical idealism does not base its proof on the absolute nature of thinking, but relies on the argument of naïve realism, when followed to its logical conclusion, cancels itself out. How does the matter appear when we have recognized the absoluteness of thinking?

[29] Let us assume that a certain perception, for example, red, appears in my consciousness. To continued observation, this percept shows itself to be connected with other percepts, for example, a definite figure and with certain temperature- and touch-percepts. This combination I call an object belonging to the sense-perceptible world. I can now ask myself: Over and above the percepts just mentioned, what else is there in the section of space in which they appear? I shall then find mechanical, chemical and other processes in that section of space. I next go further and study the processes I find on the way from the object to my sense organs. I can find movements in an elastic medium, which by their very nature have not the slightest in common with the percepts from which I started. I get the same result when I go on and examine the transmission from sense organs to brain. In each of these fields I gather new percepts, but the connecting medium which weaves through all these spatially and temporally separated percepts is thinking. The air vibrations which transmit sound are given to me as percepts just like the sound itself. Thinking alone links all these percepts to one another and shows them to us in their mutual relationship. We cannot speak of anything existing beyond what is directly perceived except what can be recognized through the ideal connections of percepts, that is, connections accessible to thinking. The way objects as percepts are related to the subject as percept -- a relationship that goes beyond what is merely perceived -- is therefore purely ideal, that is, it can be expressed only by means of concepts. Only if I could perceive how the percept object affects the percept subject, or, conversely, could watch the building up of the perceptual pattern by the subject, would it be possible to speak as modern physiology and the critical idealism based on it do. Their view confuses an ideal relation (that of the object to the subject) with a process which we could speak of only if it were possible to perceive it. The proposition, "No color without a color-sensing eye," cannot be taken to mean that the eye produces the color, but only that an ideal relation, recognizable by thinking, subsists between the percept "color" and the percept "eye". Empirical science will have to ascertain how the properties of the eye and those of the colors are related to one another, by what means the organ of sight transmits the perception of colors, and so forth. I can trace how one percept succeeds another in time and is related to others in space, and I can formulate these relations in conceptual terms, but I can never perceive how a percept originates out of the non-perceptible. All attempts to seek any relations between percepts other than thought relations must of necessity fail.